Fluorine compounds are used in many manufacturing processes. In particular, they are widely used in the manufacture of semiconductors. Fluorine compounds are among the more costly of the more commonly used chemicals in manufacturing processes and, moreover, are among the more environmentally detrimental of such chemicals. Accordingly there is a need for recovering fluorine compounds used in manufacturing processes so that they not cause environmental problems and also so that they may be reused.
One method currently used by industry for ensuring that fluorine compounds are not released to the environment involves combustion of the fluorine compounds contained in an effluent stream. While this method effectively destroys the fluorine compounds thus preventing environmental pollution, it also makes it impossible to reuse the fluorine compounds. This method is also disadvantageous because it generates waste gases such as hydrogen fluoride and nitrogen oxides which require further treatment. Furthermore, combustion processes require fuel and oxidant to operate, adding further operating and capital costs to the manufacturing operation.
Another method currently used by industry for the recovery of fluorine compounds is adsorption wherein the fluorine compounds are adsorbed onto adsorbent under elevated pressure and desorbed from the adsorbent under vacuum. This method is disadvantageous because very high power consumption is needed to carry out the requisite pressurization and depressurization. Moreover, the fluorine compound mixture from the desorption generally requires further purification before the components of the mixture can be reused. Still further, adsorption processes do not have the flexibility to deal with the dramatic changes in fluorine compound concentrations and flow rates which characterize manufacturing effluent streams such as those from a semiconductor manufacturing plant.
Accordingly it is an object of this invention to provide an improved fluorine compound recovery system.
It is another object of this invention to provide an improved fluorine compound recovery system which does not generate significant amounts of waste gas.
It is a further object of this invention to provide a fluorine compound recovery system which can produce fluorine compound product without need for significant further separation or purification for reuse.
It is yet another object of this invention to provide a fluorine compound recovery system which can operate effectively in spite of large changes in fluorine compound concentrations and flow rates in the stream to be treated.